IFC 4.3.x development IfcSphere Semantic definitions at the entity

The IfcSphere is a Construction Solid Geometry (CSG) 3D primitive. It is a solid where all points at the surface have the same distance from the center point. The inherited Position attribute defines the IfcAxisPlacement3D and provides:

  • SELF\IfcCsgPrimitive3D.Position: The location and orientation of the axis system for the primitive. 
  • SELF\IfcCsgPrimitive3D.Position.Location: The center of the sphere.
  • SELF\IfcCsgPrimitive3D.Position.Position[3]: The z axis points at its positve direction towards the north pole, and by its negative directions towards the south pole.


EXAMPLE  Figure 1 illustrates geometric parameters of the sphere. The sphere is positioned within its own placement coordiante system relative to the object coordinate system. The origin is the center of the sphere.

Figure 1 — Sphere geometry

NOTE  Definition according to ISO/CD 10303-42:1992
A sphere is a CSG primitive with a spherical shape defined by a centre and a radius.

NOTE  Entity adapted from sphere defined in ISO 10303-42.

HISTORY  New entity in IFC2x3.

Texture Use Definition

Textures are aligned facing upright with origin at the back (+Y direction) revolving counter-clockwise. Textures are stretched or repeated to the extent of the circumference at the equator according to RepeatS and RepeatT.

Figure 2 illustrates default texture mapping with a clamped texture (RepeatS=False and RepeatT=False). The image on the left shows the texture where the S axis points to the right and the T axis points up. The image on the right shows the texture applied to the geometry where the X axis points back to the right, the Y axis points back to the left, and the Z axis points up.

Side Normal Origin X Origin Y Origin Z S Axis T Axis
Side +Y 0 +Radius 0 (-X, then curving counter-clockwise) (+Z, then curving towards top)

Figure 2 — Sphere textures Attributes

# Attribute Type Description
LayerAssignmentSET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.

> IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added.

> IFC4 CHANGE  The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
StyledByItem SET [0:1] OF IfcStyledItem FOR Item Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.

> IFC2x3 CHANGE  The inverse attribute StyledByItem has been added.
1 Position IfcAxis2Placement3D The placement coordinate system to which the parameters of each individual CSG primitive apply.
Dim INVALID The space dimensionality of this geometric representation item, it is always 3.
2 Radius IfcPositiveLengthMeasure The radius of the sphere. Entity inheritance

dot_inheritance IfcSphere IfcSphere IfcCsgPrimitive3D IfcCsgPrimitive3D IfcSphere->IfcCsgPrimitive3D IfcCsgPrimitive3D_children 4 more... IfcCsgPrimitive3D_children->IfcCsgPrimitive3D IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcCsgPrimitive3D->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem Formal representations

ENTITY IfcSphere
 SUBTYPE OF (IfcCsgPrimitive3D);
	Radius : IfcPositiveLengthMeasure;